Grounding of electrical cable trays and supports

Metallic cable trays and their supports must be properly grounded and bonded to ensure electrical safety, provide a low-impedance path for fault currents, and comply with NEC and industry standards.

Grounding Requirements

All metallic cable trays must be grounded regardless of whether they are used as an Equipment Grounding Conductor (EGC). The grounding ensures that any fault current is safely conducted to earth, preventing electric shock and equipment damage (NEC Article 250. 96).

Cable trays can serve as the EGC in qualifying installations, but the tray must meet minimum metal cross-sectional area requirements based on the circuit's fault protection rating (Table 392. 60(A)). Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 A, and aluminum trays above 2000 A.

Bonding Practices

Bonding connects all metallic components of the tray system to maintain equal electrical potential. This includes connecting tray sections, supports, and any installed EGCs. Bonding prevents voltage differences that could cause arcing, reduces electromagnetic interference, and ensures continuity under fault conditions.

Grounding clamps or tin/zinc-plated connectors are recommended to mechanically and electrically secure EGCs to the tray. Bare copper conductors should not be used in aluminum trays in moist environments due to corrosion; insulated conductors with exposed bonding points are preferred. Equipment Grounding Conductor (EGC) OptionsTray as EGC: The tray itself can serve as the EGC if it meets NEC requirements and is electrically continuous.

Parallel EG

C: A single conductor cable can run along the tray as a common EGC for all circuits, bonded to the tray at intervals.

Individual Cable EG

Cs: Each multi-conductor cable may have its own EGC, which should be bonded to the tray sections for mechanical stability and electrical continuity.

Practical Considerations

Ensure electrical continuity across all tray sections and supports. Use insulated or plated connectors to prevent corrosion and maintain reliable bonding. Maintain proper separation of power and data cables to reduce interference.

Regularly inspect grounding and bonding connections to ensure long-term safety and compliance.

Follow NE

C Article 392 for tray installation, fill limits, and grounding requirements. Proper grounding and bonding of cable trays and supports not only protects personnel and equipment but also enhances system reliability, reduces fire hazards, and ensures compliance with electrical codes.